It has been banned in pre-AI style manuals.

I write “therefore” therefore I am an AI.

I’m curious about this (I’m not a native speaker). What alternative would you use when you want to emphasize a cause-effect relationship, in an engineering context for example?

“Most times A happens before B, but this order it’s not guaranteed. Therefore, there is a possibility of {whatever}.”

Alternatives that come to mind are “as a consequence”, “as a result”, “this means that”, but those are all more verbose, not less.

A simple “so” could work, but it would make the sentence longer, and the cause-effect relationship is less explicit I think.

Just take it out. It makes no difference. You set it up so clearly in your first example.

"Most times A happens before B, but in this order it’s not guaranteed, so there is a possibility of {whatever}."

That forces me to keep the phrase going though, which is my usual problem when both the A,B, and whatever are already long winded.

As I mentioned in a reply to the other comment, this often means you have your ordering mixed up.

As an example, here's what you original statement said (with some grammar corrected):

"Most times A happens before B, but the order is not guaranteed. Therefore, there is a possibility of {whatever}."

Here it is if you lead with the important outcome and provide the justification after, using a non-restrictive relative clause to add the fact that A often happens before B:

"There is a possibility of {whatever}, as, while A happens before B, the order is not guaranteed."

In my opinion, this is clearer in intent. It provides the important information immediately and then justifies it immediately after. The original sentence provides information without context and then contextualizes it using "therefore", which comes across a bit pedantic to me. I am a native American English speaker though, and the tone of prose does vary depending on the culture of the person reading it.

I disagree with v_____.

"He didn't send the letter. The lawsuit was dropped."

"He didn't send the letter therefore the lawsuit was dropped."

Two very different examples. "therefore" in the second example communicates a causal effect from the independent clause that isn't present in the first example.

I'm sure one could argue that context clues could imply that same connection and therefore "therefore" is redundant but I just don't agree with the premise.

Therefore is reasonable in that case, though it still reads a bit clumsy. "The lawsuit was dropped" seems like the most important part of that blurb, so leading with it flows better. "The lawsuit was dropped after he didn't send the letter" is so much nicer. You get to the point and explain it immediately after instead of giving the reader information you have to contextualize after. "Therefore" just reads as pedantic and overbearing in most situations in my opinion (and I guess my teacher's opinion too).

English class is about as relevant to the average office worker's professional communication as art class is to a professional paint crew.

Correct. Pearls before swine.

Therefore isn't empty verbiage. It's just communication, it's a conjunctive adverb. Therefore implies causation or at least some connection between clauses.

I could see arguing that starting a sentence or paragraph with "Therefore, " repeatedly in one essay is empty but tbh your teacher just sounds jaded.